High Temperature Nitrification Synthesis Of Si₂N₂O And Its Optimization On The Properties Of Refractory

Oxygen silicon nitride is a kind of excellent high temperature structural materialsand refractory materials with excellent oxidation resistance, thermal shock resistance,corrosion resistance, creep resistance and high strength in high temperature, highdensity, low inflation and other excellent properties. Silicon oxynitride compositematerial and silicon nitride composites have similar mechanical and thermal properties,however, the oxidation resistance, thermal shock resistance and chemical stability ofsilicon oxynitride composites are better than that of silicon nitride composites. Atpresent, the research on silicon oxynitride is very limited, therefore, this paper studiedthe effect of various process factors on the high temperature nitrification of siliconoxynitride and carried on microstructure observation to the synthesized powder.Meanwhile, adding the synthesized powder to several kinds of refractory materials toexplore the possibilities of silicon oxynitride to improve the performance of refractorymaterials. And the conclusions are as follow:(1)The best technology of synthesis of silicon oxynitride is the mass ratio ofelemental silicon and the analytically pure silica is7:5.72, the reaction temperature is1460℃×3h, the raw material granularity is d50=5.551μm; the content of Si2N2O in thesamples synthesized with high purity quartz glass powder and analytically pure silicapower and quartz powder as silica source was87%,89%,86%and that with silica fumeas silica source was79%; in the synthesized samples, the grain morphology of Si2N2Ois columnar or layer, the grain length is4-7μm.(2) The reaction mechanism of synthesis of silicon oxynitride with silicon andsilica as raw materials under nitrogen atmosphere is random nucleation and subsequentgrowth. The most probable mechanism function for the reaction system isG()=[-ln(1-)]4, the corresponding differential equation is f()=1/4(1－)[－ln(1－)]-3, the apparent activation energy is710.86kJ/mol and the pre exponential factor A is7.76×1023min-1. (3) The various performance of MgO-SiC-C shaped refractory is better when the qvalue is0.37and the content of graphite and silicon carbide is5%and15%; thesynthesized Si2N2O powder improved the physical properties, oxidation resistance andslag resistance of MgO-SiC-C shaped refractory; the various performance ofMgO-SiC-C shaped refractory is better when the content of Si2N2O is1%.(4) Adding suitable amount of silicon oxynitride can improve the strength, slagresistance and oxidation resistance and the microstructure of iron runner material; thesuitable amount of silicon oxynitride added to the iron runner material is1-2%.(5) Adding suitable amount of silicon oxynitride can improve the performance ofAl2O3-SiC-C shaped refractory; the physical properties, oxidation resistance and slagresistance of Al2O3-SiC-C shaped refractory are better while Si2N2O addition amount is1%,2%and3%respectively; the magnesium aluminate spinel generated of the edge ofcorundum particles of the reaction layer in slag resistance samples and MgO in blastfurnace slag in Al2O3-SiC-C shaped refractory prevent slag to further erode the inside ofcorundum particles. Adding2%Si2N2O can promote to generate more apparent SiO2balls whose diameter are about3μm in the pores of oxide layers of Al2O3-SiC-C shapedrefractory, thus blocking pores and preventing the spread of the oxygen to oxide testspecimens; adding3%Si2N2O into Al2O3-SiC-C shaped refractory can promote toproduce more silicon oxide into the slag, therefore improving the viscosity of slag andweakening the slag erosion and penetration to the samples.